The present invention relates to the backing on surface coverings, preferably carpet backings, and more particularly relates to the use of polymeric microspheres in the backings of surface coverings, such as carpets and resilient floor coverings.
Generally, surface coverings have a backing layer wherein a surface of the backing layer rests against the sub-surface or sub-floor on which it is applied, such as a concrete or wood floor.
The commercial carpet market in United States is approximately 80% 12 ft. wide broadloom carpets and 20% modular tiles and 6 ft. wide roll goods. The most popular modular size in U.S. is 18″×18″ and to a much lesser extent 24″×24″ and 36″×36″ modular sizes are also used. Modular tiles are predominantly vinyl backed.
The modular tiles are gaining more and more of market share in the office environment because: (1) Modular tiles allow easy access to subfloor for utilities; (2) Less disruption in office work during installation or replacement; (3) Easy to reconfigure modular furniture in open office planning situations with carpet modules; (4) Ease of transport in multi-story buildings; (5) Unlimited design flexibility; (6) Easy to install and remove; (7) Durable and cost effective; (8) Ability to replace damaged tile selectively; and (9) High performance.
The most predominantly used material for 6 ft. wide roll goods in U.S. is based on polyvinyl chloride, often referred to as “vinyl”.
The 6 ft. vinyl backed roll goods are also increasing their market share in healthcare, institutional and other markets due to their higher performance over broadloom carpet, ability to provide wall to wall moisture barrier due to chemically weldable properties of vinyl at carpet seams, superior dimensional stability, easy to transport, install and remove carpet, as well as it's lower cost based on life cycle.
The carpet tiles and 6 ft. wide roll goods have been growing rapidly in the last 25 years. They are different in properties and end use applications compared to traditional 12 ft. wide SBR latex backed carpets. The SBR latex chemistry is aqueous system (water based) where as the vinyl chemistry is non-aqueous. SBR latex backed carpets are hard backed and as such, they are glued to the floor or installed over a cushioned padding. SBR latex backed carpet as compared to vinyl backed modular tiles or 6 ft. roll goods are in a totally different category. This is due to the fact that one can not take SBR latex backed 12 ft. wide carpet and cut it into 18″×18″ carpet tiles or 6 ft. wide roll goods and expect the same functionality.
The construction and components of carpet tiles and 6 ft. vinyl backed roll goods are completely different. The vinyl backed products are engineered products with a different cross section and use a non-woven fiberglass fleece or scrim.
The unique properties of vinyl backed products such as superior dimensional stability, double moisture barrier, high wet tuft bind, chemically weldable carpet seams, ability to withstand repeated wet cleanings are not exhibited by 12 ft. wide SBR backed carpet and hence it is clear that SBR backed 12 ft. wide broadloom carpet and 18″×18″ vinyl backed carpet tiles or 6 ft. wide vinyl backed roll goods are different products. The modular tiles and 6 ft. roll goods are offered with hardback backings as well as cushioned backings.
Recently, cushion backed products are increasing in demand because they offer better under foot comfort and hence better ergonomics as well as better appearance retention of the face of the carpet.
The 6 ft. wide, vinyl cushion backed roll goods and 18″×18″ vinyl cushion backed modular products are available in the market place today. These vinyl foam backed products predominantly use closed-cell chemical foam. The closed-cell foams are achieved by the use of a blowing agent which blows the original thickness by 3 to 4 times when subjected to relatively high temperatures generally between 380° F.-400° F. Since the production of closed-cell chemical foam generally requires relatively high blow ratios (3-4) and high temperatures it can not be applied and be blown directly on the back of the carpet. Hence, production on vinyl foam backed modules and 6 ft. roll goods is currently achieved in the following three steps.                Step-1 Apply pre-coat to the tufted carpet.        Step-2 Produce closed-cell PVC foam as a separate process.        Step-3 Laminate previously pre-coated carpet with pre-manufactured PVC foam closed-cell PVC foam sheet.        
Further, there are some disadvantages of this three step process. They are as follows:    (1) Poor dimensional stability because process requires hot lamination at elevated temperatures (approx. 350° F.-360° F.) of vinyl foam to the pre-coated carpet under extremely well controlled tension conditions. In actual manufacturing it is very difficult to control precise temperatures, tensions, and orientation of the textile product, such as tufted carpet without distortion.
Further, this process is not capable of incorporating non-woven fiberglass fleece or scrim in the secondary backing composite. The net result is this process produces a dimensionally unstable product. In order to overcome this difficulty, the carpet is sold with very aggressive, factory applied adhesive. This adhesive is so aggressive that removal of the carpet is time consuming and very expensive. Many times, the primary backing is removed but the secondary backing still adheres to the sub-floor, due to the poor delamination strength and/or dimensional stability.    (2) The delamination strength of secondary foam backing is often low and uneven due to difficulty in precise process control.    (3) The chemically blown foam still has some open cells which is confirmed by moisture absorption tests (usually 6-10%).
The present invention removes many, if not all of the disadvantages of currently used methods of manufacturing particularly vinyl foam backed carpet tiles and 6 ft. vinyl foam backed roll goods. Further, the present invention preferably uses a one step process that is easy to control, and where elevated temperatures are not required. Further, fiberglass stabilizers are in use in the backing structure and thus imparts superior dimensional stability. The PVC pre-coat layer provides a moisture barrier at the base of the tufts and wet-on-wet lamination of the adhesive coat and the foam coat imparts superior delamination strength.